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The Telecom Digest for August 18, 2012
Volume 31 : Issue 197 : "text" Format
Messages in this Issue:
fios questions (Michael)
Re: fios questions (HAncock4)
Re: fios questions (John Levine)
Re: Did anyone ever figure out where "E&M" came from? (Bill Horne)

====== 30 years of TELECOM Digest -- Founded August 21, 1981 ======

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Date: Fri, 17 Aug 2012 02:18:06 -0700 (PDT) From: Michael <michael.muderick@gmail.com> To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org. Subject: fios questions Message-ID: <b395de08-dc5a-4155-9ecb-b537bd6fe581@w9g2000yqe.googlegroups.com> I may finally make the switch from copper/DSL to FIOS. I have a couple of questions. I use many of the older Western electric/ATT phones in my house. They work with the old 90volt ringers. Will there be any problems with FIOS regarding this? How about the polarity sensitive dials? Will they still work? Will they still be polarity sensitive? What about the backup battery in the FIOS box.? Does it need regular replacing? How often? Does Verizon charge for that? How long does it last in a power failure? Thanks so much for your answers.
Date: Fri, 17 Aug 2012 08:19:54 -0700 (PDT) From: HAncock4 <withheld@invalid.telecom-digest.org> To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org. Subject: Re: fios questions Message-ID: <26705c03-9f59-4409-b15e-77787727a6d7@c19g2000vbb.googlegroups.com> On Aug 17, 5:18 am, Michael <michael.muder...@gmail.com> wrote: > What about the backup battery in the FIOS box.? > Does it need regular replacing? How often? Does Verizon charge for > that? How long does it last in a power failure? A friend with FIOS says the backup battery lasts about three hours in a power failure. Unfortunately, when a severe storm knocks out power for much longer periods there is no phone service until power is restored. Friends with cable-TV provided phone service also report no phone service during power outages. FWIW my traditional land-line has always remained available even during extended power outages.
Date: 17 Aug 2012 15:45:35 -0000 From: "John Levine" <johnl@iecc.com> To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org. Subject: Re: fios questions Message-ID: <20120817154535.79338.qmail@joyce.lan> >couple of questions. I use many of the older Western electric/ATT >phones in my house. They work with the old 90volt ringers. Will >there be any problems with FIOS regarding this? Assuming you don't have too many of them, you should be OK. > How about the polarity sensitive dials? Will they still work? Will they still be >polarity sensitive? That's a characteristic of the phone, not the phone line. They'll work as well as they ever did. If they all stop working at once, you'll need to make a one time fix and swap the wires where the FIOS box connects to the home wiring to make the polarity the same as it used to be. > What about the backup battery in the FIOS box.? >Does it need regular replacing? Yes. > How often? Every few years. > Does Verizon charge for that? No, you're on your own. They don't do battery replacements. > How long does it last in a power failure? A while. Hours, perhaps, depending on how old the battery is and how much stuff you have attached. R's, John
Date: Fri, 17 Aug 2012 05:06:06 -0600 From: Bill Horne <bill@horneQRM.net> To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org. Subject: Re: Did anyone ever figure out where "E&M" came from? Message-ID: <k0l8iv$gam$1@dont-email.me> On 8/15/2012 7:37 PM, Will wrote: > Fred Goldstein<fgoldstein.SeeSigSpambait@wn2.wn.net> wrote in > news:20120312221919.705485468@mailout.easydns.com: > >> On Sun, 11 Mar 2012, Bill Horne wrote, >> >>> I've been searching through various archives this morning, without >>> success, trying to find out if anyone ever figured out the origin of >>> the "E& M" signalling lead designations. When I took the D-18 course >>> at New England Telephone, I read that the designations might have come >> >from old circuit diagrams for telegraph equipment, but that nobody >>> knew for sure. >> >> I'd put this into one of those "lost to history", but I tend to give >> some credence to the story told in various sources, including David >> Talley's "Basic Telephone Switching Systems" (1969), which said, >> >> "The E and M system received its name from historical designations >> found on old circuit drawings. The E refered to the middle "e" in >> received and the M from the m in transmit." >> >> But it's also possible that those were just mnemonics. The drawings >> of some circuit or other at sone point in time may have simply >> labeled the leads A,B,C,... and those two happened to be E and >> M. Then somebody came up with the mnemonics. After all, if I wanted >> to name the two signaling (not bearer) leads, ear and mouth would not >> be the first things that come to mind. > > I suspect that the E&M leads, as known today for two state signalling, > may have been in addtion to other signaling leads used on early in-band > signaling equipment. For example, while I never worked on DLL equipment > at the AT&T Toll office where I once worked in the late 1970's, DLL > equipment, not to be confused with the more typical 2W loop extension > repeater circuits in common use, were designed to work with signaling > units to convert two state E&M signaling (B& X Types) to loop& ground > start operations. I recall circuit layout models showing a K option for > DLL equipment. Unfortunately I never had the opportunity to work on such > circuit layout designs, having been broken in in B, E, and F type SF, > and auxiliary units. Latter DS1 carrier equipment. > While trunk signaling equipment employed E&M leads, loop signaling units > used an A&B lead designation, along with SX/SX1 when a DC signaling > component was employed. Will, I have a different recollection, so I'm going to provide some background details that I hope will make things more clear. E&M signalling equipment was almost never used with equipment that provided dial tone. There were exceptions, but they were very rare, and were limited to providing Foreign Exchange "trunk" lines to PBX customers. In those cases, the FX line was often carried on L-Carrier between cities, using SF signalling. In those designs, an intermediate signalling apparatus was required, such as the Western Electric SD96371 Ground Start - E&M converter, which would allow the central office to provide ground-start signalling. Now, I need to make a distinction between shared-use, i.e., toll trunks, and dedicated private lines. The most common use of E&M signalling in New England Telephone, outside of switching, was for private line signalling, and this is where the "A&B" or "SX/SX1" designations were most common. In the Sixties and Seventies, it was common for large PBX owners to pay for "Tie" lines between their PBX locations, so as to cut down on the cost of having employees dial phone calls from one building to another. Since most Tie Lines were carried on copper pairs - they went into private buildings, after all, and it was extremely uncommon to see T-Carrier outside "Ma Bell" in those years - the tie line signalling was done with "DX" equipment, i.e., with the same "Duplex" repeater sets that had been in use for Telegraph lines since the beginning of the Western Union company or before. The DX signalling units, most commonly the EMX-1 and EMX-2, were duplex-to-E&M converters. The "A" and "B" leads connected to these units were carried on the simplex leads of the four-wire tie lines, and in order to derive simplex connections, the four-wire circuits were wired to 120C or similar "Repeating Coils", which were actually center-tapped transformers with a 1:1 turns ratio. IIRC, the center taps of the 120C coils were labelled "SX" and "SX1" at the frame, so that may be the cause of the confusion here: the "A" and "B" leads coming from an EMX-1 or EMX-2 unit were wired to the "SX" and "SX1" lugs of the 120C coils on the frame. The EMX signalling units included provisions to "strap", or bypass, various resistance values that were built in to the units, so as to compensate for ground resistance. Of course, the use of a derived simplex signalling path obviated the need for that, and although it was theoretically necessary to measure the loop resistance of the derived pair and strap the EMX units to account for it, few techs bothered. The point, though, is that the capability was /there/, which makes it clear that the DX signalling method was invented in the telegraph world, where ground-return signalling was the norm, and if you look at early schematic drawings of "DX" units, you'll see that the "E" and "M" leads were used exactly as they are today. Bill, who works the graveyard shift and sometimes is able to check Usenet. -- Bill Horne (Remove QRM from my address to write to me directly)
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